JPH11129154A - Polishing device for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device for a semiconductor wafer to polish a film, formed on a semiconductor wafer, in a flat. SOLUTION: A plurality of air jet nozzles 48, 50, and 52 are formed in a carrier 24. Air is injected from air nozzles 48, 50, and 52 according to the thickness of the film of a semiconductor wafer W positioned opposite to air nozzles 48, 50, and 52. By controlling an air pressure of the air at each of air nozzles 48, 50, and 52, the film is polished in a flat by controlling a polishing amount in the semiconductor wafer W. Namely, in this invention, film thickness distribution of the film is previously obtained and an air pressure is controlled such that when the film is polished, the air pressure of the air nozzle 48 positioned opposite to the thick section part of the film thickness is increased and reversely, the air pressure of the air nozzles 50 and 52 opposite to the thin section part of the film thickness is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for polishing a semiconductor wafer, and more particularly to a chemical mechanical polishing method (CMP).
al Mechanical Polishing)
The present invention relates to a semiconductor wafer polishing apparatus for polishing an oxide film (thin film) formed by a (chemical vapor deposition) apparatus.

[0002]

2. Description of the Related Art A semiconductor wafer polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 8-339979 supplies a pressurized fluid between a carrier and a semiconductor wafer, and applies pressure to the semiconductor wafer by a polishing pad. To polish the semiconductor wafer. Such a polishing apparatus is a thin film (insulating film: SiO) formed by an oxide film forming apparatus such as a CDV apparatus.
_This is a device for polishing ₂ ), and obtains flatness of the thin film by uniformly polishing the surface of the semiconductor wafer.

[0003]

As shown in FIG. 4, the thickness of the thin film 3 formed on the semiconductor wafer 1 together with the wiring pattern 2 is not uniform in the plane of the semiconductor wafer 1, Are thick near the center and thinner toward the outer periphery.

When the semiconductor wafer 1 having such a film thickness distribution is polished by the above-mentioned conventional polishing apparatus, the thin film 3 is polished uniformly in the surface of the semiconductor wafer 1, so that the non-uniform film thickness is eliminated. Therefore, there is a disadvantage that the thin film 3 cannot be polished flat.
The present invention has been made in view of such circumstances, and has as its object to provide a semiconductor wafer polishing apparatus that can polish a thin film formed on a semiconductor wafer evenly.

[0005]

According to the present invention, in order to attain the above object, a pressure air layer is formed between a carrier holding a semiconductor wafer and the semiconductor wafer, and a pressure air layer transmitted from the carrier to the carrier is formed. In a semiconductor wafer polishing apparatus for transmitting a pressing force to a semiconductor wafer through the pressure air layer and pressing the semiconductor wafer against a polishing cloth to polish a thin film formed on the semiconductor wafer, a central portion of the pressure air layer The method is characterized in that the thin film is polished by controlling the amount of polishing in the surface of the semiconductor wafer by changing the air pressure between the semiconductor wafer and the peripheral portion.

According to the present invention, the thin film is polished by controlling the amount of polishing in the surface of the semiconductor wafer by changing the air pressure between the central portion and the peripheral portion of the pressure air layer. That is, the present invention sets the air pressure at the center of the pressure air layer facing the thick portion of the semiconductor wafer to be high, and conversely, the peripheral portion of the pressure air layer facing the thin portion. Set the air pressure low. As a result, the thick portion is polished more than the thin portion, and as a result, the thin film is polished flat.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a semiconductor wafer polishing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of an apparatus for polishing a semiconductor wafer according to an embodiment of the present invention. The semiconductor wafer polishing apparatus 10 shown in FIG. 1 mainly includes a polishing table 12 and a wafer holding head 14. Polishing surface plate 1
2 is formed in a disk shape, and an upper surface thereof is
Is provided. In addition, a spindle 18 is connected to a lower portion of the polishing table 12, and the spindle 18 is connected to an output shaft (not shown) of a motor 20. Motor 20
Is driven, the polishing platen 12 rotates in the direction of arrow A, and slurry is supplied from a nozzle (not shown) onto the polishing pad 16 of the rotating polishing platen 12. The wafer holding head 14 is provided so as to be vertically movable by an elevating device (not shown), and is moved upward when a semiconductor wafer to be polished is set on the wafer holding head 14. Further, when polishing the semiconductor wafer, the wafer holding head 14 is moved down and pressed against the polishing cloth 16.

FIG. 2 is a longitudinal sectional view of the wafer holding head 14. The wafer holding head 14 shown in FIG. 1 includes a head body 22, a carrier 24, a guide ring 26, a polishing surface adjustment ring 28, a rubber sheet 30, and the like. The head body 22 is formed in a disk shape,
The motor 2 is rotated in the direction of arrow B by a motor (not shown) connected to the motor 2. The air supply path 3 is provided in the head body 22.
4 and 36 are formed. The air supply path 34 extends outside the wafer holding head 14 as shown by a two-dot chain line in the figure, and is connected to an air pump (AP) 40 via a regulator (R) 38A. The air supply path 36 is connected to a pump 40 via a regulator 38B.

The carrier 24 is formed in a substantially columnar shape, and is arranged coaxially with the head main body 22 below the head main body 22. Further, a donut-shaped concave portion 25 is formed on the lower surface of the carrier 24, and a porous plate (sucking portion) 42 having air permeability is accommodated in the concave portion 25. An air suction path 44 communicates with the porous plate 42. The air suction passage 44 extends outside the wafer holding head 14 as shown by a two-dot chain line in the drawing, and is provided with a suction pump (SP: su).
ction pump) 46. Therefore, when the suction pump 46 is driven, the semiconductor wafer W is sucked by the porous plate 42 and held by suction on the lower surface of the porous plate 42. The porous plate 42 has a number of air passages therein, and for example, a porous plate made of a sintered body of a ceramic material is used.

As shown in FIGS. 2 and 3, an air ejection hole 48 is formed on the bottom surface of the carrier 24 coaxially with the center axis of the carrier 24. Air ejection holes 50, 50 are formed around the air ejection hole 48, and air ejection holes 52, 52 (only two are shown in FIG. 2) are formed outside the air ejection holes 50, 50. The air ejection hole 48 communicates with the outside of the wafer holding head 14 as shown by a two-dot chain line in FIG. 2, and is connected to the pump 40 via a regulator 38C. Therefore, the compressed air from the pump 40 is blown out to the air chamber 54 between the carrier 24 and the semiconductor wafer W via the air blowout hole 48. Thereby, the air chamber 5
4, a pressure air layer is formed, and the pressing force of the carrier 24 is transmitted to the semiconductor wafer W via this pressure air layer. The semiconductor wafer W is pressed against the polishing pad 16 by the pressing force transmitted through the pressure air layer.

The air ejection hole 48 communicates with a cross-shaped air guide groove 49A formed on the bottom of the carrier 24, as shown in FIG. The air guide groove 49A communicates with an annular air guide groove 49B. The air guide groove 49B is formed so as to surround the central portion of the semiconductor wafer W being polished. Therefore, the air blown out from the air blowing holes 48 is blown out through the air guide grooves 49A and the air guide grooves 49B, so that the vicinity of the center of the semiconductor wafer W is pressed against the polishing pad 16 by the air pressure. Will be. The pressing force can be adjusted by adjusting the amount of compressed air supplied by the regulator 38C.

The air ejection holes 50 are formed at 180 ° intervals as shown in FIG. The air ejection holes 50 are communicated with the outside of the wafer holding head 14 as shown by a two-dot chain line in FIG.
Is connected to the pump 40 via the. Therefore, the compressed air from the pump 40 is blown into the air chamber 54 through the air blowing holes 50, 50. By the way, as shown in FIG. 3, the air ejection hole 50 communicates with an annular air guide groove 51 formed on the bottom surface of the carrier 24. The air guide groove 51 is formed with a radius approximately half of that of the semiconductor wafer W. Therefore, the air ejection holes 5
Since the air blown out from 0 and 50 is blown out through the air guide groove 51, the vicinity of the substantially central portion in the radial direction of the semiconductor wafer W is pressed against the polishing pad 16 by the air pressure. The pressing force can be adjusted by adjusting the amount of compressed air supplied by the regulator 38D.

The air ejection holes 52 are formed at four locations at 90 ° intervals as shown in FIG. Are connected to the outside of the wafer holding head 14 as shown by a two-dot chain line in FIG.
It is connected to an air pump 40 via a regulator 38E. Therefore, the compressed air from the pump 40 is blown into the air chamber 54 through the air blowing holes 52, 52. By the way, as shown in FIG. 3, the air ejection hole 52 communicates with an annular air guide groove 53 formed on the bottom surface of the carrier 24. This air guide groove 53 is
Each of the air ejection holes 52 is divided into
1 and are formed concentrically with the guide groove 51 outside.
Are formed along the outer peripheral portion of the semiconductor wafer W. Therefore, the air blown out from the air blowout holes 52, 52 is blown out through the air guide grooves 53, 53.
Pressed to. The pressing force can be adjusted by adjusting the amount of compressed air supplied by the regulator 38D.

In FIG. 2, one rubber sheet 30 is arranged between the carrier 24 and the head main body 22. This rubber sheet 30 is formed in a disk shape with a uniform thickness. The rubber sheet 30 is fixed to the lower surface of the head main body 22 by an annular stopper 58, and the rubber sheet 3
0 is the central portion 30A and the outer peripheral portion 30B with respect to the stopper 58.
And it is divided into two. The central portion 30A of the rubber sheet 30 presses the carrier 24, and the outer peripheral portion 30B presses the polishing surface adjustment ring 28.

A rubber sheet 3 is provided below the head body 22.
A space 60 which is hermetically sealed by the central portion 30 </ b> A and the stopper 58 is formed. The air supply path 36 communicates with the space 60. Therefore, when compressed air is supplied from the air supply path 36 to the space 60, the central portion 30A of the rubber sheet 30 is elastically deformed by air pressure and presses the upper surface of the carrier 24. Thereby, a pressing force of the semiconductor wafer W against the polishing pad 16 can be obtained. Also,
If the air pressure is adjusted by the regulator 38B, the pressing force (polishing pressure) of the semiconductor wafer W can be controlled.

The guide ring 26 is formed in a cylindrical shape, and is disposed coaxially with the head main body 22 below the head main body 22. In addition, the guide ring 26 is attached to the rubber sheet 3.
0 is fixed to the head main body 22. A polishing surface adjusting ring 28 is disposed between the guide ring 26 and the carrier 24. A retainer ring 62 for preventing the semiconductor wafer W from jumping out is attached to a lower inner peripheral portion of the polishing surface adjusting ring 28.

An annular space 64 is formed in the lower outer peripheral portion of the head main body 22 so as to be sealed by the outer peripheral portion 30B of the head main body 22 and the rubber sheet 30 and the like. This space 6
4 communicates with the air supply path 34. Therefore, when compressed air is supplied from the air supply path 34 to the space 64, the outer peripheral portion 30B of the rubber sheet 30 is elastically deformed by air pressure and presses the annular upper surface of the polishing surface adjustment ring 28. As a result, the annular lower surface of the polishing surface adjusting ring 28 is
Pressed to 6. The pressing force of the polishing surface adjusting ring 28 can be controlled by adjusting the air pressure with the regulator 38A.

In FIG. 2, the wafer holding head 1
4 is provided with a differential transformer 70 for detecting a polishing amount of the semiconductor wafer W. The bobbin 68 of the differential transformer 70 is attached to the tip of an arm 76 extending in the rotation axis direction of the wafer holding head 14 from the inner surface of the polishing surface adjustment ring 28. The core 66 of the differential transformer 70 is provided on the upper surface of the carrier 24 and at a position where the central axis of the core 66 is coaxial with the rotation axis of the wafer holding head 14. The differential transformer 70 can detect the amount of vertical movement of the carrier 24 with respect to the lower surface of the polishing surface adjustment ring 28, that is, with respect to the polishing surface of the semiconductor wafer W. Thereby, the polishing amount of the semiconductor wafer W can be detected. Note that a groove 78 for inserting the arm 76 is formed in the carrier 24.

Next, the operation of the semiconductor wafer polishing apparatus 10 configured as described above will be described. First, before starting the polishing, the thickness of the thin film formed on the semiconductor wafer W to be polished is measured in advance, and the film thickness distribution in the plane of the semiconductor wafer W is obtained. The film thickness distribution obtained in the present embodiment is as shown in FIG.

After obtaining the film thickness distribution, polishing of the semiconductor wafer W is started. First, after raising the wafer holding head 14, the suction pump 46 is driven to suck and hold the semiconductor wafer W to be polished on the porous plate 42. Next, the wafer holding head 14 is lowered, and the lowering movement is stopped at a position where the contact surface of the polishing surface adjustment ring 28 contacts the polishing pad 16. Then, the suction pump 46 is stopped to release the suction of the semiconductor wafer W, and the semiconductor wafer W is placed on the polishing pad 16.

Next, when the pump 40 is driven to emit compressed air from the air ejection holes 48, 50, 52, the compressed air is released from the air guide grooves 49A, 49B, 51, 53, 5
3 and quickly supplied to the air chamber 54. As a result, a pressure air layer is quickly formed in the air chamber 54. Then, the air pressure of the compressed air ejected from the air ejection holes 48, 50, 52 is adjusted by the regulators 38C to 38E.
Is adjusted for each of the air ejection holes 48, 50, 52. That is, in the present embodiment, the thin film of the semiconductor wafer W is
As shown in the figure, since the thickness is large near the center of the semiconductor wafer W and becomes gradually thinner toward the outer periphery, the air pressure from the air ejection hole 48 is P1, and the air ejection hole 5 is large.
Assuming that the air pressure from 0 is P2 and the air pressure from the air ejection holes 52 is P3, adjustment is made so that P1>P2> P3. As a result, the vicinity of the center of the semiconductor wafer W having a large thickness is polished more, and the polishing is performed so that the polishing amount decreases toward the outer periphery. Therefore, the thin film is polished flat.

Next, compressed air from the pump 40 is supplied to the space 60 via the air supply path 36,
The central portion 30A is elastically deformed by the internal air pressure to press the carrier 24. Thereby, the semiconductor wafer W
Is pressed against the polishing pad 16 via a pressure air layer.
The pressing force at this time is the same as that of the regulator 38C.
Since the air pressure is adjusted by .about.38E, the vicinity of the central portion of the semiconductor wafer W is large and becomes smaller toward the outer peripheral portion. Then, the air pressure is adjusted by the regulator 38B, and the rubber sheet 3 with respect to the carrier 24 is adjusted.
The pressing force of 0 is kept constant.

Next, compressed air from the pump 40 is supplied to the space 64 via the air supply path 34, and the outer peripheral portion 30B of the rubber sheet 30 is elastically deformed by internal air pressure to press the polishing surface adjusting ring 28. . As a result, the lower surface of the polishing surface adjusting ring 28 and the lower surface of the retainer ring 62 are
6 at the same time. Thereafter, the polishing platen 12 and the wafer holding head 14 are rotated so that the semiconductor wafer W
Start polishing.

Then, the polishing amount of the semiconductor wafer W during polishing is detected by the differential transformer 70, and when the detected polishing amount of the semiconductor wafer W reaches a preset polishing target value, a polishing end signal is sent. Then, the semiconductor wafer polishing apparatus 10 is stopped. Thus, polishing of one semiconductor wafer W is completed, and the thin film is polished flat.

In the present embodiment, the air ejection holes 4
8, 50 and 52 are formed in the carrier 24 to adjust the air pressure in three stages. However, the present invention is not limited to this. Four or more types of air ejection holes are formed to adjust the air pressure. Can be adjusted in multiple stages, the polishing amount control in the plane of the semiconductor wafer W can be subdivided,
Thereby, the flatness of the thin film can be further improved.

[0026]

As described above, according to the semiconductor wafer polishing apparatus of the present invention, the air pressure at the center of the pressure air layer facing the thick portion of the semiconductor wafer is set high, Since the air pressure at the peripheral portion of the pressure air layer facing the thin portion is set low, the thin film can be polished flat.

[Brief description of the drawings]

FIG. 1 is an overall structural view of a semiconductor wafer polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a wafer holding head applied to the semiconductor wafer polishing apparatus of FIG. 1;

FIG. 3 is a bottom view of the carrier of the wafer holding head shown in FIG. 2;

FIG. 4 is a schematic diagram for explaining a film thickness distribution of a thin film of a semiconductor wafer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Semiconductor wafer polishing apparatus 12 ... Polishing platen 14 ... Wafer holding head 22 ... Head body 24 ... Carrier 30 ... Rubber sheet 38A-38E ... Regulator 40 ... Air pump 48,50,52 ... Air ejection hole 49A, 49B, 51 , 53 ... Air guide groove

Claims (2)

[Claims] 1. A pressure air layer is formed between a carrier holding a semiconductor wafer and a semiconductor wafer, and a pressing force transmitted from the pressing means to the carrier is transmitted to the semiconductor wafer via the pressure air layer. Thus, in a semiconductor wafer polishing apparatus for polishing a thin film formed on a semiconductor wafer by pressing the semiconductor wafer against a polishing cloth, by changing the air pressure between the central portion and the peripheral portion of the pressure air layer, the inside of the semiconductor wafer A polishing apparatus for polishing a semiconductor wafer, wherein the polishing is performed on the thin film by controlling an amount of polishing. 2. An apparatus for polishing a semiconductor wafer according to claim 1, wherein an air pressure at a central portion of said pressure air layer is set higher than an air pressure at a peripheral portion of said pressure air layer.